This invention is related to flame retardant polyamide compositions having improved physical properties, excellent molding characteristics and improved arc tracking resistance.
Polyamides represent a family of commercially available polymers characterized by the presence of recurring amide groups in the polymer chain and generally noted for their excellent physical properties for a variety of end uses including the formulation of molding compositions. Of the polyamides, Nylon 6, produced by the polymerization of e-caprolactam, and Nylon 66, produced by the condensation reaction of adipic acid and hexamethylene diamine, account for a major share of commercial polyamide molding compositions.
Various means have been proposed for imparting a flame-resistant character to polyamides--these means, include the incorporation into the polyamide composition of halogenated products to which certain inorganic oxides, such as those derived from cadmium, arsenic, bismuth and antimony are frequently added (French Pat. No. 1,568,952 and U.S. Pat. No. 4,247,450). The use of halogenated products to impart fire-resistance to polyamides is well known; U.S. Pat. No. 3,403,036 to Hindersinn et al describes the incorporation of bis(hexachlorocyclopentadieno)cyclooctane, optionally in combination with a suitable metal oxide, in nylon compositions. U.S. Pat. No. 4,194,072 describes the incorporation of bis(hexachlorocyclopentadieno)cyclooctane in formulations of Nylon 6, Nylon 66 and Nylon 612 with selected metal oxides. However, it has been found that articles manufactured from these compositions of the prior art exhibit an unacceptable arc tracking resistance and in numerous applications, in particular for the electrical and electronics industry, the compositions cannot meet commercial requirements.